Opposite actions of oxytocin and vasopressin in the development of cocaine-induced behavioral sensitization in mice.

Subchronic administration of cocaine induces behavioral sensitization (increasing hypermotility) to a challenge dose of the drug administered 72 h after the cessation of treatment. The effects of repeated administration of the neurohypophyseal hormones oxytocin (OXT) and arginine8-vasopressin (AVP) on the development of behavioral sensitization induced by subchronic treatment with cocaine were investigated in mice. Repeated treatment of OXT and AVP did not modify the locomotor stimulatory effect of the challenge dose of cocaine in cocaine-naive control animals. OXT in a dose of 0.5 microgram (sc) augmented the cocaine-induced behavioral sensitization. In contrast, AVP (0.005-0.5 microgram/mouse, sc) dose dependently attenuated the development of sensitization to the hypermotility-inducing effect of cocaine. The results suggest that the behavioral sensitization induced by cocaine can be modulated in opposite directions by neurohypophyseal hormones.